Guide to Conventional Treatment Options for Fleas and Ticks

Recently, Hemopet provided a guide for companion pet parents on choosing or making more all-natural treatment options to mitigate tick infestations. Full disclosure, we do prefer that route. However, we realize that some companion pet parents will choose more conventional flea and tick treatment options such as prescription oral treatments, spot-on treatments or collars for their pets. Inherently, these come
with their own set of risks that companion pet parents will need to speak about with their veterinarians,
and determine if they are safe for their pets and household.

One problem that crops up is that the options are endless and confusing. Products are competing for our attention and dollars. Companies compare their product option to a competitor – but usually not all other options. Eventually, as a companion pet parent, you throw your hands in the air out of frustration and just choose something. We get it.

We have summarized the listed adverse reactions and precautions from the product labels. Importantly, please note that the current labels include the warning about seizures, behavioral changes and death, as required by the U.S. Food and Drug Administration (FDA), the Center for Veterinary Medicine (CVM), the U.S. Environmental Protection Agency (EPA), and the European Medicines Agency

The Big 3 Pests: Mosquitoes, Fleas and Ticks

First, let’s do an overview of the big three pests:

#1. Mosquitoes spread heartworm disease to dogs and sometimes cats. NOTE: Hemopet does advocate for heartworm preventatives to be used accordingly in the environment in which companion dogs reside. We have discussed primarily heartworm preventatives at the end of this post.

#2. Fleas can carry and spread tapeworms (intestinal parasitic worms) and cat scratch fever along with other diseases. They can also cause reactions such as flea allergy dermatitis.

#3. Ticks can spread Lyme Disease, Rocky Mountain Spotted Fever, Tularemia, anaplasmosis, babesiosis, and ehrlichiosis, among other diseases.

General “Good to Knows”

#1. Fleas – There are two primary categories of flea treatments: killing existing adult fleas and insect growth regulators that disrupt flea development from larvae to adults. Adult fleas do not lay eggs for 36-48 hours after their first blood meal. 

#2. Many pharmaceutical drugs that combat mosquitoes, fleas and ticks are broad-spectrum. Meaning: they take care of one problem and another. The simplest explanation is that many heartworm preventatives also cover intestinal worms. The FDA indicates (approves) the use of pharmaceutical medications for certain conditions. So, a drug may also cover another pest, but the FDA has not approved it for that use. This is often referred to as “off label use”.

#3. In general, the FDA primarily regulates what goes “inside” the body of a companion pet and some topicals depending on the class of drug. The EPA oversees the majority of flea and tick topicals and collars because the chemicals used are usually considered pesticides. You will notice a difference in the level of detail provided to consumers such as adverse reactions due to the different regulations between the two agencies. 

#4. Many animal health manufacturers combine heartworm preventatives with flea and tick treatment options. NOTE: TO REDUCE POTENTIAL ADVERSE REACTIONS AND TO KNOW THE CAUSE OF A POTENTIAL ADVERSE REACTION, HEMOPET PREFERS GIVING HEARTWORM PREVENTATIVES SEPARATE FROM FLEA AND TICK TREATMENTS. We would separate them by 15 days. For instance, heartworm preventatives given on the first of the month, and flea and tick on the 15th of the month.   

#5. Remember: there is a difference between killing and repelling pests. 

Isoxazoline Class of Drugs

According to the FDA:

  • The FDA considers products in the isoxazoline class to be safe and effective for dogs and cats but has provided more information on recent reported adverse events. 
  • Isoxazoline products have been associated with neurologic adverse reactions, including muscle tremors, ataxia, and seizures in some dogs and cats.
  • Although many dogs and cats haven’t had neurologic adverse reactions, seizures may occur in animals without a prior history.

In addition to the FDA warning above, we summarize the types of side effects and adverse reactions that have been reported.

Side Effects/Adverse Reactions: Vomiting, decreased appetite, diarrhea, lethargy, drowsiness, polydipsia, flatulence, dry skin, hair loss, moist dermatitis, scabs/ulcerated lesion, itching, elevated ALT,  hypersalivation, rapid breathing, incoordination, seizures, and weight loss.

Primarily Heartworm

FDA-approved antiparasitic drugs such as ivermectin (Heartgard), selamectin (Revolution), milbemycin oxime (Interceptor) and moxidectin (Advantage Multi) have been tested and found safe for MDR1-affected dogs when given at the prophylactic heartworm preventative dosage level. However, we still caution companion pet parents who may have a dog with the MDR1 gene mutation.

Other Flea and Tick Products

Some of these products are highly reactive and toxic to cats and rabbits. Refer to product inserts for specific adverse effects. Companion pet parents will need to decide if they want to introduce these into their households and weigh the potential adverse reactions to pets and humans.

Side Effects/Adverse Reactions: Skin irritation such as redness, scratching, or other signs of discomfort, gastrointestinal signs such as vomiting or diarrhea, digestive upset, temporary hair loss at application site with possible inflammation, diarrhea with or without blood, anorexia, lethargy, salivation, tachypnea,  muscle tremors. urticaria, erythema, ataxia, fever, and rare reports of death.


The information provided here is intended to provide companion pet parents with the background necessary to decide if a product is right for their household and for the health of their pet companions.

Yes; Hemopet does prefer all-natural treatment options. A companion dog or cat could still introduce fleas or ticks to your household by tracking them in and shaking them off. The window between pest kill time and infestation or attachment with many of the conventional options is anywhere between two to twelve hours. Therefore, you will still need to be vigilant and check your pets. Granted, ticks are tiny before they attach and may be difficult to find. 

Best of luck!  


Palmieri, Valerie, et al. “Survey of Canine Use and Safety of Isoxazoline Parasiticides.” Veterinary Medicine and Science, vol. 6, no. 4, 2 June 2020, pp. 933–945., doi:10.1002/vms3.285,

Suzuki, Tomohiro, et al. “The Effects of Fipronil on Emotional and Cognitive Behaviors in Mammals.” Pesticide Biochemistry and Physiology, vol. 175, June 2021, doi:10.1016/j.pestbp.2021.104847,

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